1. Field of the Invention
The present invention generally relates to display apparatuses, and more particularly to a display apparatus in which a plurality of image data read from a video memory (or a display memory) are supplied to a display unit wherein the image designated by the image data is displayed on a screen thereof.
2. Prior Art
Conventionally, a known display apparatus is controlled to display an image on a screen by use of a central processing unit (CPU). Such color image display apparatus includes a video random access memory (VRAM) therein which pre-stores a plurality of image data each of which corresponds to a display dot arranged on the screen. The color image data are read from the VRAM and are converted into analog color signals of R, G and B (hereinafter, analog color signals of R, G and B will be referred to as RGB signals). The RGB signals with synchronizing signals are supplied to a CRT color display unit wherein the image designated by the RGB signals are displayed on the screen thereof.
Meanwhile, the image data stored in the VRAM must be changed in order to change the image displayed on the screen of the display unit in the conventional display apparatus. In this case, the CPU gives access to the VRAM wherein all image data are displaced by other image data, hence, much time must be required for displacing the image data. In addition, it is impossible to simultaneously write the image data into the VRAM within the conventional color image display apparatus. As a result, the conventional display apparatus suffers a problem in that it is impossible to displace the image displayed on the screen with a high speed.